The invention relates to the field of face masks. More particularly, the invention relates to the field of face masks for use in gas delivery applications.
In traditional face mask design, breathable gas or aerosol drug is directly delivered into a chamber of the face mask, while at the same time, the exhalation gas generated from the nose or the mouth of the wearers will enter into the chamber. Therefore, the substantial amount of the breathable gas or aerosol drug to be inhaled by the wearer is not enough since the concentration of the breathable gas or aerosol drug is diluted with the exhalation gas.